ch6: idk why yennefer wants her womb back so much tbh

Question 1

draw a labelled diagram of the digestive system (4)

Answer 1

google docs
oesophagus: connected to top of stomach
stomach: connected to small intestine
small and large intestines: connected to each other
liver shown as larger than the stomach with gall bladder shown under liver
gall bladder: connected to the small intestine via bile duct
pancreas: connected to small intestine via pancreatic duct

Question 2

draw a labelled diagram showing the interconnections between the liver, gall bladder, pancreas and small intestine (2)

Answer 2

google docs

Question 3

describe the digestion of food in the human digestive system (6)

Answer 3

digestion begins in the mouth
chewing food → smaller parts → ↑ surface area
starch breaks down to maltose by amylase

proteins break down to polypeptides by pepsin in the stomach
HCl provides optimum pH medium for enzymatic activity
churning in stomach causes mechanical digestion by mixing the enzymes & food

bile salt secreted from gallbladder to emulsify lipid droplets
pancreas:
secrete endopeptidase to break down polypeptides into amino acids
secrete pancreatic lipase to break down lipids into glycerol & 3 fatty acids
secrete pancreatic amylase to break down maltose into glucose
secrete sodium bicarbonate to neutralise acidic chyme to pH 8 for optimum pH medium for enzymatic activity

some final digestion into monomers is associated with epithelial cells of small intestine
peristalsis mix food with digestive juices
circular muscle contraction prevents backward movement of food
longitudinal muscle contraction moves food along gut

Question 4

outline the digestion, absorption and assimilation of proteins in humans (6)

Answer 4

proteins must be digested into smaller molecules for absorption
protein → polypeptides by pepsin secreted by the stomach
pH 2
polypeptide → amino acids by pancreas secreted by the pancreas
pH 8

amino acids are absorbed into capillaries by diffusion and active transport through the villi and microvilli in the small intestine
blood carries amino acids thru the body → diffuse or absorbed into cells by active transport

assimilation: amino acid becomes part of cell
cells use amino acid for protein synthesis in ribosomes

Question 5

explain the importance of enzymes/hydrolysis to human digestion (8)

Answer 5

digestion = the breakdown of large molecules → small molecules
for diffusion & absorption → bloodstream → cells
physical breakdown is not enough → need chem breakdown of food
enzymes are required to ↑ rate of digestion
biological catalyst
allow digestion to occur at body temp

enzymatic digestion is a sequential process
amylase: polysaccharides → disaccharides → monosaccharides
starch → maltose → glucose
protease: protein → polypeptides → amino acids
lipase: lipid → triglyceride → glycerol & 3 fatty acids

specific location for each reaction with specific conditions
diff enzymes have diff optimal pH
e.g. stomach pepsin pH 2
most enzymes work extracellularly

Question 6

explain how the structure of a villus in the small intestine is related to its function (7)

Answer 6

villus has a large surface area to volume ratio
microvilli ↑ surface area for absorption

thin epithelial layer → short diffusion distance → products of digestion can easily pass thru
channel proteins located in plasma membrane → facilitated diffusion
large number of mitochondria → provide ATP
protein pumps in microvilli membrane → active transport
pinocytosis occurs at epithelial layer

network of capillaries inside each villus
transport absorbed sugars & amino acids away from small intestine → blood flow maintain conc gradient
lacteal transport fatty acids away from small intestine

Question 7

describe the role of the stomach in digesting proteins (5)

Answer 7

protein digestion begins in stomach
acid env denatures other proteins + kill bacteria + activate pepsin
gastric glands in stomach release digestive juice that contains pepsin
pepsin catalyse protein hydrolysis
hydrolysis breaks large proteins into shorter polypeptides
churning mix pepsin with proteins

Question 8

explain the relationship between structure and function of arteries, capillaries and veins (8)

Answer 8

arteries:
thicc walls → withstand ↑ blood pressure
narrow lumen → maintain ↑ blood pressure
smooth muscle layer → contract to maintain pressure & reduce friction
elastic fibres in outer layer → give wall strength & flexibility

capillaries:
thin epithelial layer of 1 cell only → short diffusion distance → faster diffusion
extensive branching → ↑ surface area for exchange of materials
small diameter → fit between cells/tissues + ↑ oxygen diffusion from red blood cells
pores → allow lymphocytes/plasma to exit

veins:
thin walls → allow skeletal muscles to exert pressure on it
wide lumen → allow ↑ vol of blood to pass
thin muscle fibres in outer layer → provide structural support
valves → prevent backflow

Question 9

explain the roles of the atria and ventricles in the pumping of blood (4)

Answer 9

atria collect blood from vena cava & pulmonary vein while ventricles are contracting
pump blood into ventricles

ventricles pump blood into arteries
thick muscular walls → high pressure
left ventricle pump blood to systems
right ventricle pump blood to lungs

heart valves working with atria & ventricles → keep blood moving

Question 10

explain how circulation of the blood to the lungs and to other systems is separated in humans and what the advantages of this separation are (8)

Answer 10

double circulation: heart has separate pumps for lungs & other systems
deoxygenated blood pumped to the lungs & oxygenated to other organs
kept separate → all tissues receive blood with high oxygen content

each side of the heart has an atrium & ventricle
left ventricle pump blood to system via aorta
right ventricle pump blood to lungs via pulmonary artery
left atrium receive blood from lungs via pulmonary vein
right atrium receive blood from system via vena cava

high pressure blood would damage lungs
high pressure required to pump blood to all systems
pressure of blood returning from lungs not high enough to continue to tissues → has to be pumped again

Question 11

outline the exchange of materials between capillaries and tissues (3)

Answer 11

molecules move by diffusion down a conc gradient
nutrients move into tissues
gas exchange between tissues & capillaries
waste & excess water move from tissues into capillaries
hormones leave capillaries in target tissues to attach to receptors on cells
endocrine gland tissues release hormones into bloodstream

Question 12

outline how the rate at which the heart beats is controlled (6)

Answer 12

cardiac muscle contraction is myogenic: contract without stimulation
sinoatrial node (SA node) initiates heart contractions
located in the right atrium
electrical signal to contract transmitted from wall of the right atrium → then through walls of the ventricles

nerve impulses transmit messages to pacemaker
medulla control speed of heartbeat through nerves
one nerve ↑ rate while another ↓ it

adrenal gland produce adrenaline → accelerate heartbeat
part of the fight or flight response

Question 13

describe the action of the heart in pumping blood (5)

Answer 13

atrial systole:
atria collect blood from veins
SA node sends impulses to muscle to initiate contraction
both atria contract at the same time → blood is pushed through open atrioventricular valves into ventricles
semilunar valves are closed so that ventricles fill with blood

ventricular systole:
ventricle muscles contract
blood is pushed out through semilunar valves → into pulmonary artery and aorta
atrioventricular valves snap close

diastole:
ventricles and atria relax → ↓ pressure
semilunar valves close to prevent the backflow of blood

Question 14

explain how the direction of blood flow in the heart is controlled (2)

Answer 14

valves prevent backflow of blood
open valves allow blood to flow through
valves open when pressure is higher upstream
atrioventricular valves prevent backflow from ventricles to atria
semilunar valves prevent backflow from arteries to ventricles
closed: allow ventricles to fill with blood

Question 15

draw a labelled diagram of the human heart showing the attached blood vessels (6)

Answer 15

google docs
right and left atrium: above the ventricles and must not be bigger
than ventricles
left and right ventricle: below the atria, must have thicker walls
than atria
superior and inferior vena cava: connected to right atrium
pulmonary artery: from right ventricle to lungs
pulmonary vein: from lungs to left atrium
aorta: large artery from left ventricle out of heart;
atrioventricular valves: between both atria and ventricles
semilunar valves: in aorta and pulmonary artery

Question 16

outline the mechanisms of defence against pathogens in humans (7)

Answer 16

1st line:
skin: physical barrier
sebaceous glands secrete sebum
mucous membrane: trap & remove + contain lysosomes that destroy pathogens
stomach acid: extreme pH inhibits growth of pathogens
inflammation: cause swelling and fever to inhibit the pathogen

2nd line: phagocytic leukocytes identify pathogens as foreign → ingest by endocytosis

3rd line: specific lymphocytes recognise specific antigens → clone themselves
produce antibodies that attach to specific antigens → form antigen-antibody complex → stimulate destruction of pathogen

Question 17

outline how leukocytes defend the body against pathogens (6)

Answer 17

recognise pathogens → phagocytes engulf pathogens by endocytosis
migration to tissues by squeezing out of capillaries

each pathogen has a specific antigen:
lymphocytes produce antibodies by reacting to the specific antigen
lymphocytes make clones by mitosis & ↑ total no. of specific antibodies
antibody joins to specific antigen & destroys them

Question 18

outline how antibiotics offer protection from certain forms of infectious disease (4)

Answer 18

kill/inhibit bacteria growth
bacteria processes blocked but not processes in eukaryotic cells
block metabolic pathways, DNA replication/transcription/translation, ribosome functioning, cell wall formation
do not protect against viruses bc no metabolism
antibiotics fail to protect if bacteria have resistance

Question 19

discuss the cause, transmission and social implications of AIDS (8)

Answer 19

cause:
by HIV: AIDS is observed syndrome when final stages of infection develop
no. of lymphocytes ↓ over years
↓ immunity
other illnesses develop

transmission:
body fluids from an infected person transmits HIV, which could progress to AIDS
transmitted by blood transfusions, sharing needles, sexual intercourse
can be prevented by using condoms correctly
transmitted from mother to child across the placenta, during childbirth & breastfeeding
↑ incubation period → no awareness of infection → ↑ transmission
small amount of individuals do not have cell receptors and do not develop AIDS

social implications:
death of parents → orphans
expenses in treatment → poverty
unemployment
discrimination/homophobia
family & friends suffer grief
lack of edu → unequal occurrence of HIV/AIDS
gov/social/faith-based services → inequality of treatment

Question 20

explain the need for a ventilation system and the mechanism of ventilation of lungs (8)

Answer 20

need:
most cellular respiration is aerobic → drives the need for gas exchange and oxygen
gas exchange depends upon a ventilation system
exchanges oxygen and CO2 between inhaled air and blood stream
alveoli provide surface area for gas exchange
ventilation system maintains a high concentration of oxygen in the alveoli
bloodstream links alveoli to cells

inhalation:
air enters lungs through trachea, bronchi & bronchioles
external intercostal muscles contract → ribs move upwards/outwards
diaphragm contracts → flattens
↑ vol of thorax → ↓ pressure → allow air to enter passively

exhalation:
air exits lungs through trachea, bronchi & bronchioles
external intercostal muscles relax → ribs to move downwards/inwards
abdominal muscles contract to push diaphragm up → diaphragm relaxes → returns to original domed position
↓ vol of thorax → ↑ pressure → force air out of lungs

a conc gradient of oxygen between air sacs & blood needs to be maintained

Question 21

describe what happens in alveoli (4)

Answer 21

vol of alveoli ↑ as air enters alveoli during inhalation
network of capillaries in which blood flows through

gas exchange occurs
oxygen diffuses from air to blood: binds to haemoglobin in red blood cells
carbon dioxide diffuses from blood to air

type II pneumocytes secrete surfactant to prevent sides of alveoli adhering

Question 22

outline the process of gas exchange necessary for aerobic respiration (3)

Answer 22

oxygen is taken up by cells
carbon dioxide is released by cells

gases pass through a cell membrane by simple diffusion
require a concentration gradient
no need ATP

red blood cell has large surface area to volume ratio

Question 23

describe the structure of the ventilation system, including the alveoli (8)

Answer 23

ventilation occurs within the lungs
trachea divides to form 2 bronchi
divide to form bronchioles
several divisions of bronchioles
alveoli connected to bronchioles
lined with cilia
have c-shaped cartilage

diaphragm and intercostal muscles
alveoli
small
many alveoli → ↑ surface area → ↑ absorption rate
thin epithelial layer of 1 cell only → ↓ diffusion distance → ↑ absorption rate
surrounded by a dense network of capillaries → ↓ diffusion distance + steep conc gradient → ↑ absorption rate
surfactant on the inside of the alveolus produced by type II pneumocyte → allows oxygen to dissolve → diffusion of oxygen down conc gradient

Question 24

draw a labelled diagram to show the human ventilation system (4)

Answer 24

google docs
trachea
bronchi
bronchioles
lungs
alveoli: enlarged as inset
diaphragm
intercostal muscles
abdominal (wall) muscles

Question 25

distinguish between ventilation, gas exchange and cell respiration (4)

Answer 25

ventilation: inhalation & exhalation
involves muscle activity

gas exchange: movement of carbon dioxide & oxygen
between alveoli & blood in capillaries
between blood in capillaries & cells

cell respiration: release of energy from glucose
aerobic cell respiration occurs in mitochondria

Question 26

draw a labelled diagram of a motor neuron (5)

Answer 26

google docs

Question 27

explain how nerve impulses pass from one neuron to another neuron (8)

Answer 27

action potential reaches the pre-synaptic membrane
Ca channels open & Ca2+ diffuse into pre-synaptic neuron
neurotransmitter vesicles fuse with the plasma membrane & releases the neurotransmitters by exocytosis
synapse = gap between neurons
neurotransmitters diffuse across the synaptic cleft & binds with the receptors on the post-synaptic membrane
ion channels open & Na+ enters → post-synaptic neuron depolarises
neurotransmitters are broken down by enzymes → stops effects on post-synaptic membrane

Question 28

explain how an impulse passes along the membrane of a neuron (8)

Answer 28

the resting membrane is polarised
interior is -70 mV & is relatively negative compared to outside
more Na+ outside, more K+ inside

nerve impulses are action potentials propagated along the axons of neurons
neurotransmitter attaches to receptor site → initiating transmission
opens Na+ channels → Na+ rush into cell → depolarisation
local currents cause action potential
Na+ channels shut and K+ channels open → K+ rush out of cell → restore polarised state of membrane
sodium-potassium pumps maintain polarity and restore resting potential

process is repeated along the length of the neuron
Na+ diffuse between region with action potential and region at resting potential
myelin permits saltatory conduction + speed up transmission

Question 29

outline the role of the sodium-potassium pump in maintaining the resting potential (2)

Answer 29

pumps 3 Na+ out of axon and 2 K+ in each time
results in charge difference between inside and outside → outside is pos relative to inside
needs ATP

Question 30

explain the effect of neonicotinoid pesticides in insect synapses in the central nervous system (3)

Answer 30

similar to nicotine chemically
bind to acetylcholine receptors
not broken down by acetylcholinerase → blocks acetylcholine binding → causes paralysis

Question 31

explain the principle of homeostasis with reference to the control of body temperature (9)

Answer 31

homeostasis = maintaining a constant internal env within narrow limits
e.g. body temp, blood pH, blood glucose, water, CO2 conc
involves hormonal/nervous control
negative feedback
deviation from the norm → trigger mechanisms to restore norm

body temperature in mammals must be maintained at a constant level for enzymes
37℃
hypothalamus is the centre of thermoregulation
sends impulses to the body to ↑/↓ temp

temperature receptors in skin transmit impulses to the hypothalamus
heat is transferred from blood
if temp ↑ → vasodilation of arterioles → ↑ heat loss
if temp ↓ → vasoconstriction of arterioles → ↓ heat loss
if skin temp ↑ → release sweat from sweat glands in the skin
evaporation of water cools body
shivering ↑ heat production in muscles
hair becomes erect and traps air
behavioural mechanism: reduce activity → ↓ body temp

Question 32

explain briefly the principle of negative feedback in homeostasis (2)

Answer 32

change in env is detected
initiate response to bring the system back to normal state
when normal state is reached → response is stopped → prevents overreaction
internal env fluctuates around norm

Question 33

describe the control of blood glucose concentration in humans (6)

Answer 33

the level of glucose in blood is regulated by homeostasis
negative feedback mechanism

pancreas ɑ-cells produce glucagon that ↑ blood glucose levels
produced when blood glucose levels ↓
stimulate liver cells to break down glycogen → glucose
glucose released in blood to return levels to normal

pancreas β-cells produce insulin that ↓ blood glucose levels
produced when blood glucose levels ↑
stimulate liver cells to absorb glucose → glycogen/use for respiration → return levels to normal

Question 34

distinguish between type I and type II diabetes (5)

Answer 34

google docs

Question 35

outline how leptin controls appetite (3)

Answer 35

leptin inhibits appetite
secreted by adipose tissue
level is controlled by amount of adipose tissue
amount of adipose tissue ↑ → blood leptin conc ↑
targets cells in hypothalamus

Question 36

describe melatonin’s role in mammals (2)

Answer 36

produced by pineal gland
controls circadian rhythms
affect sleep-wake cycles
production is controlled by amount of light detected by the retina
high secretion in the dark

Question 37

outline the role of hormones in the menstrual cycle (8)

Answer 37

follicle-stimulating hormones (FSH) released from pituitary gland
stimulates follicle growth in the ovary
oocytes mature

cells of growing follicle produce estrogen
stimulates more FSH receptors on follicle cells so respond more to FSH
positive feedback
signals endometrium to thicken
final maturation of follicles

rapid ↑ levels of estrogen
stimulate secretion of luteinizing hormone (LH)
LH spike stimulate ovulation
stimulate remaining follicle → develop into corpus luteum
stimulate corpus luteum → secrete progesterone

progesterone stimulate maintenance of endometrium in prep for embryo implantation
no pregnancy → corpus luteum disintegrates
↓ in progesterone → breakdown in endometrium
progesterone inhibit FSH and LH release
neg feedback

Question 38

the role of sex hormones in the development of secondary sex characteristics (4)

Answer 38

females
enlargement of breasts
growth of pubic & underarm hair
widening of hips

males
growth of facial, underarm, chest & pubic hair
enlargement of the larynx & deepening of the voice
↑ muscle mass
enlargement of the penis

Question 39

draw a labelled diagram of the human adult male reproductive system (5)

Answer 39

google docs
testis: inside scrotum
epididymis: adjacent to testis and connected to sperm duct
sperm duct: double line connecting
testis/epididymis to urethra
seminal vesicles: sac branched off sperm duct
prostate gland: positioned where sperm duct connects with urethra
urethra: double line linking bladder to end of penis;
penis: urethra passing through it

Question 40

draw a labelled diagram of the human adult female reproductive system (5)

Answer 40

google docs

Question 41

draw a labelled diagram of a mature sperm cell (4)

Answer 41

google docs
head and midpiece
tail: 4x length of the head and containing fibres
acrosome: distinct structure near front of head
nucleus: occupy more than half the width or length of head
mitochondria: repetitive structures inside membrane of mid piece
centriole: between head and midpiece
plasma membrane: single line covering whole cell
microtubules

Question 42

outline the process of in vitro fertilisation (IVF) (6)

Answer 42

hormones are given to stop ovulation
hormones are injected in mother to stimulate the development of multiple follicles
induce the maturation of eggs
retrieve eggs thru minor surgery
sperms are collected in vitro
in vitro fertilisation of egg & sperm
fertilised egg is grown in medium → implant in uterus

Question 43

discuss the ethical issues associated with IVF (8)

Answer 43

pros:
infertile couples can conceive
offspring is genetically related to them
conscious decision to have children → responsible parents
screening of embryos → ↓ chances of inherited diseases/chromosomal defects
↑ reproductive age
cancer patients can harvest ova/sperm b4 chemo
production of extra embryo can be used for research

cons:
potential risks from drug treatment
against some religious beliefs
infertility may be heritable → passed onto offspring
expensive